« Previous | Contents | Next »
Listen
Annex B: Traffic Calming Measures Suitable for Urban Roads
Road Humps
Road humps are the most effective traffic calming measure available for reducing speed. They are also the most severe as they force the driver to slow down. There are many different types of road hump, including round top, flat top, raised junctions (speed tables) and speed cushions.
Speed cushions have been introduced in order to overcome concerns about discomfort and delay expressed by bus companies and the emergency services resulting from the use of flat and round top road humps. Their design allows these larger wider vehicles to straddle the cushion thereby reducing delay and discomfort.
Concerns have been expressed about the potential for low vehicles to ground on road humps and cushions. Following research into this, a maximum height of 75mm is recommended: this may need to be lower for very short or narrow cushions (see TA Leaflet 2/96).
Traffic Advisory Leaflet 3/91 (Speed Control Humps Scotland, England and Wales) gives guidance on the use of road humps and Traffic Advisory Leaflet 1/98 specifically deals with speed cushions.
Road Narrowing Measures
Narrowing the carriageway is also considered an effective way of reducing vehicle speeds. It is less intrusive for the driver but nevertheless requires drivers to negotiate an obstacle, thus encouraging them to slow down.
Chicanes, Build-outs, Overrun areas and Traffic Islands all have the effect of reducing the width of the carriageway. Chicanes achieve the biggest reduction in vehicle speeds with Traffic Islands achieving the least reduction.
Guidance on the use of Chicanes, Build-outs, Overrun areas and Traffic Islands can be found in Traffic Advisory Leaflet 11/94.
Gateways
Gateways are typically used in rural areas on the approach to villages and other areas where vulnerable road users can be expected. One definition of a Gateway is 'combinations of natural or man-made features at the entry to, or exit from, areas where the rules or drivers' expectations change, such as the introduction of speed limits' (Institution of Highways and Transportation, 1997).
Gateway features may be constructed on the verge, footway or cycle track. One of the main features will usually be vertical elements at the sides of the road as a strong visual cue for drivers. It is also possible for a gateway to span the carriageway. In common with all traffic calming features, a gateway may include paving, grass or other cover; pillars, planters, walls, rails or fences, trees, shrubs and other plants.
Traffic Advisory Leaflet 11/94 gives guidance on the use of gateways, also Traffic Advisory Leaflet 9/99 (20 mph Speed Limits and Zones).
Road Markings
The use of road markings can also have some effect in persuading drivers that a slower speed is appropriate. Measures include centre hatching, changing the colour of the road surface, dragon's teeth that are sometimes used as part of a gateway feature and carriageway roundels that are used in conjunction with upright speed limit signs as an additional measure to emphasise the speed limit in force.
Rumble Devices
Rumble devices are also sometimes used. These may be in the form of rumble strips or areas that have a vibratory and audible effect that alerts the driver that extra care is needed. It should be noted that because of the vibration and noise these should not be placed close to residential areas. Traffic Advisory Leaflet 11/94 gives further advice on the use of rumble devices.
A new type of rumble device known as rumblewave surfacing has recently been developed. This has a sinusoidal profile and provides similar noise and vibration within vehicles but less external noise, making it more suitable for use near residential areas. Traffic Advisory Leaflet 1/05 gives further advice on rumblewave surfacing.
The Consultation process
Full consultation must take place before any traffic calming measures are installed. For road humps section 37(1) of the Roads (Scotland) Act 1984 requires consultation with the chief officer of police. In addition, Regulation 3 of The Road Humps (Scotland) Regulations 1998 requires consultation with the fire authority, the Scottish Ambulance Service NHS Trust and organisations representing road users. Further guidance is provided in SODD Circular No 9/1998.
For all other traffic calming The Roads (Traffic Calming) (Scotland) Regulations 1994 require consultation with the police, fire and ambulance services, and organisations representing road users or people who are likely to be affected.
« Previous | Contents | Next »